1. Field of the Invention
The present invention relates to an imaging apparatus. More particularly, the present invention relates to a complementary metal oxide semiconductor (CMOS) image sensor for use in, e.g., a camera-equipped mobile phone, a digital camera, a video camera, and others.
2. Description of the Related Art
In general, a white defect and a black defect due to, e.g., a manufacturing process are apt to be produced in an image sensor. In a single-plate color camera adopting an RGB Bayer arrangement, as a method of correcting a signal of a defective pixel, substitution processing using median filtering is known (see, for example, Jpn. Pat. Appln. KOKAI Publication No. 2006-238060 or Jpn. Pat. Appln. KOKAI Publication No. 09-247548). This method corrects a signal of a defective pixel in real time without using a memory. Further, a method of utilizing the average value of peripheral pixels around a defective pixel to substitute the signal of the defective pixel (see, for example, Jpn. Pat. Appln. KOKAI Publication No. 2004-112736) or a method of substituting a signal of a defective pixel by a maximum value (a signal having a maximum level) or a minimum value (a signal having a minimum level) of peripheral pixels (see, for example, Jpn. PCT National Publication No. 2005-528857) has been proposed.
However, any of the above-explained methods cannot judge whether a defective pixel is a defective pixel in a vertical image pattern or a defective pixel in a lateral image pattern. Therefore, a signal of a defective pixel is substituted by an intermediate value (a signal having an intermediate level) of signals of peripheral eight signals having the same color by median filtering, or substituted by a maximum value or a minimum value of signals of peripheral eight pixels having the same color, or substituted by the average value of upper and lower or right and left two pixels having the same color. Therefore, there is a problem that a resolution of the defective pixel is degraded or erroneous correction is apt to occur at an end portion (an edge portion) of an image pattern.